[contrib] don't manage merge conflict in extract-electrum.sh

Summary: After resetting the ElectrumABC github repository to its state just before the monorepo migration, then applying this patch, there should no longer be any conflicts caused by the "[electrum] initial monorepo integration" commit.

Test Plan:
Run contrib/extract-electrum.sh and check that there is no conflict and all commits are applied.
Compare the content of ./electrum and ./electrumabc-mirror (e.g. meld ./electrum ./electrumabc-mirror)

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14310